1. Field of the Invention
The present invention relates to a method of controlling synchronous drive of a plurality of pressing machines so that a position of a slide of each of the pressing machines is synchronous each other and a pressing machine usable in such a method.
The present invention also relates to a method of controlling synchronous drive of a plurality of pressing machines so that a position of a slide of each of the pressing machines is synchronous each other with a predetermined phase difference and a pressing machine usable in such a method.
2. Description of the Related Art
It has been attempted to synchronously drive a plurality of pressing machines, for example, with zero phase difference. In such a case, the output of a motor is first transmitted to the flywheel of a pressing machine, the rotational power being then transmitted to the drive shaft of the pressing machine through a clutch. The drive shaft may be in the form of a crankshaft for driving a slide (or ram). Thus, the stamping die of the pressing machine can be driven.
In the conventional phase synchronization, one of the pressing machines is used as a master machine while the other pressing machines are used as slave machines. Such a control is called xe2x80x9cmaster/slave systemxe2x80x9d.
In the prior art, the master machine controlled the velocity of the motor thereof by comparing the encode output of the motor with reference velocity information and using the difference therebetween so that the motor will be rotated with the reference velocity. In other words, the master machine did not perform the control which is based on the positional information of the crankshaft.
On the other hand, the slave machines compensatively controlled the positions thereof, based on the positional information of the crankshaft in the master machine so that the slave machines will match the master machine in phase. More particularly, an encoder was provided on each of the crankshafts to take the positional information of the rotating crankshafts in the master and slave machines. The motor of each of the slave machines was controlled to cancel the difference between the crankshaft position of the master machine and the crankshaft position of each of the slave machines.
The pressing machines may synchronously be driven with a predetermined phase difference. In this case, the motor in each of the slave machines may be controlled to create a predetermined phase difference between the crankshaft position of the master machine and the crankshaft position of each of the slave machines.
However, it is actually difficult to provide a phase difference between the master and slave machines since the rotational-position information of the master machine depends on the reference position information of the slave machines. In the first place, the prior art did not have the technical concept of phase-difference synchronous operation.
In the synchronous control mentioned above, the motor control in the slave machines will adversely be affected by any disturbance such as a load change characteristic of the master machine due to the energy released from the flywheel of the master machine on pressing. In a pressing machine having an increased load inertia, thus, it is difficult to provide an highly accurate synchronization.
In the prior art, thus, the master machine is in its characteristic driving state while the slave machines must forcibly be matched to the master machine in phase. Even though the synchronization between the master and slave machines is controlled by such a method, excessive load will be exerted to the slave machines when they are controlled in the presence of the disturbance from the master machine. This unnecessarily changes the velocity in each slave machine and degrades the accuracy in synchronization.
When the master and slave machines are to run synchronously, it is preferred that the crankshafts thereof are synchronized in phase immediately after clutch engagement.
In the prior art, thus, the crankshafts in all the pressing machines must have been stopped in a certain narrow range of angle before clutch engagement. However, such a procedure is complicated.
When the master and slave machines are to run synchronously, it is also preferred that the crankshafts thereof are synchronized with any phase difference immediately after clutch engagement.
On the other hand, when the master and slave machines are to run synchronously with phase difference, it is further preferred that the crankshafts thereof are synchronized while maintaining any phase difference therebetween, immediately after clutch engagement.
In the prior art, thus, the crankshafts of all the pressing machines must have been stopped while being aligned with one another before the clutch engagement. Alternatively, when it is required to provide a predetermined phase difference between the master and slave machines, each of the crankshafts must have been stopped with a predetermined angle corresponding to that phase difference. However, such a procedure is complicated.
When the pressing machines are synchronously running with zero phase difference, this restricts the operating cycle time for a supply device which supplies materials to the pressing machines or a delivery device which delivers products between the pressing machines. Thus, such peripheral devices have executed and been completed in operation within a limited short time period. This provides a severe limitation to the peripheral devices, leading to reduction of the maximum velocity of production in the entire press line.
It is thus an objective of the present invention to provide a method of controlling synchronous drive of a plurality of pressing machines with zero phase difference or any phase difference, which can realize an improved accuracy of synchronization without adverse affection of a load change in any one pressing machine to the remaining pressing machines as a disturbance, and to provide a pressing machine usable in such a method.
Another objective of the present invention is to provide a method of controlling synchronous drive of a plurality of pressing machines, which can effectively drive the pressing machines and avoid any overload to the pressing machines due to a transitional increase of control by reducing the positional control rate between the pressing machines immediately after clutch engagement to relieve the load on the motors, and to provide a pressing machine usable in such a method.
Still another objective of the present invention is provide a method of controlling synchronous drive of a plurality of pressing machines, which can reduce the control of the positions between the pressing machines immediately after the clutch engagement to relief the load on the motors and to avoid any increased transitional control, which can initiate the control of synchronization relating to a predetermined phase difference immediately after the pressing machines have been started with the same angle of stoppage and which can set and change the phase difference even during operation under load, and to provide a pressing machine usable in such a method.
A further objective of the present invention is to synchronously drive a plurality of pressing machines intentionally with a phase difference therebetween to extend the operating cycle time for the peripheral devices, to relieve the limitation applied to the peripheral devices and to increase the maximum velocity of production.
A further objective of the present invention is to provide a method of controlling synchronous drive of a plurality of pressing machines, in which the pressing machines will not adversely be affected by any disturbance due to a load change in any one of the pressing machines and can quickly and accurately respond to a command of motor speed change, irrespective of the engagement/de-engagement of clutch, and to provide a pressing machine usable in such a method.
A further objective of the present invention is to provide a method of controlling synchronous drive of a plurality of pressing machines, which can fully use the torque power of the motors to accelerate/decelerate the flywheels, thereby reducing time required to accelerate/decelerate the flywheels, and set-up time and waiting time, and to provide a pressing machine usable in such a method.
A further objective of the present invention is to provide a method of controlling synchronous drive of pressing machines, which can extend time required for accelerating/decelerating the pressing machine to suppress the accelerating/decelerating torques of the motors on clutch engagement, thereby changing the run velocity while maintaining the restoring function as well as the accuracy of synchronous control after the energy of the flywheels has been released on pressing, and to provide a pressing machines usable in such a method.
A further objective of the present invention is to provide a method of controlling synchronous drive of pressing machines, which does not require to maintain the clutch-off state until the flywheels reach the constant speed after the velocity has been changed, thereby enlarging the degree of freedom in the operational ability and which can further avoid any overload on the motors to drive the pressing machines more effectively, and to provide a pressing machine usable in such a method.
According to a first aspect of the present invention, it provides a method of controlling synchronous drive of a plurality of pressing machines, each of the pressing machines having a motor, a drive shaft to which a torque of a flywheel driven by the motor is transmitted through a clutch and a slide driven by the drive shaft so that a rotational position of the drive shaft of each of the pressing machines is synchronous each other, the method comprising:
a first step of setting reference velocity information of each of the motors in the pressing machines;
a second step of generating reference rotational-position information of each of the drive shafts, based on the reference velocity information;
a third step of engaging the clutch of each of the pressing machines; and
a fourth step of controlling drive of the motor in each of the pressing machines,
wherein the fourth step carried out in each of the pressing machines comprising the steps of:
detecting actual velocity information of the motor;
detecting actual rotational-position information of the drive shaft;
comparing the actual rotational-position information with the reference rotational-position information;
compensating the reference velocity information into characteristic reference velocity information of each of the pressing machines, based on a result of the comparison; and
controlling drive of the motor, based on the characteristic reference velocity information and the actual velocity information.
According to the first aspect of the present invention, the reference velocity information is set for the motor of each of the pressing machines and then used to generate the reference position information of the drive shaft of each of the pressing machines. Each reference position information is used as a virtual master signal which will not adversely be affected by the load change in either of the pressing machines. There is then determined a difference (or error) between the actual rotational-position information and the reference position information of each of the crankshafts. Such a difference is used to compensate a preset reference velocity information to determine the reference velocity information characteristic of each of the pressing machines. The motors of the pressing machines can synchronously be driven and controlled with increased accuracy, based on the reference velocity information characteristic of the respective pressing machines and the actual velocity information of the respective pressing machines.
The reference velocity information may be set in common of the motors in the pressing machines.
The first aspect of the present invention may include a step of compensating a rate of the velocity change so as to alleviate the velocity change rate, when the reference velocity information includes a velocity change. For example, even though the velocity is to be stepwise changed, the motor cannot follow the stepwise change of velocity. This causes the overload on the motor while the mechanical stress is also applied to the mechanical driving mechanism. When the speed velocity is alleviated, the motor can be driven within its rating. This provides smoother acceleration/deceleration.
The fourth step may further comprise a step of compensating the reference rotational-position information within a predetermined time period immediately after the clutch of each of the pressing machines is engaged, based on an engagement property of the clutch, which is characteristic of each of the pressing machines. Thus, the position of each of the drive shafts can smoothly be controlled immediately after clutch-on.
The third step may further comprises:
a step of detecting stoppage angle information of the drive shaft of each of the pressing machines before the clutch of each of the pressing machines is engaged; and
a step of determining an engagement sequence of the clutch of each of the pressing machines, based on the stoppage angle information of the drive shaft of each of the pressing machines, and
the engagement sequence may be determined so that the clutch of at least one of the pressing machines having a stoppage angle position of the drive shaft which is more delayed in the rotational angle of the drive shaft is engaged earlier.
Thus, the control of synchronous drive can be realized without the drive shafts of the pressing machines being stopped being aligned with a certain angle.
At this time, a clutch of one of the pressing machines may be engaged earlier than a clutch of another of the pressing machines in the third step, and a timing of clutch engagement of the other of the pressing machines may be determined based on an engagement property of the clutch of the other of the pressing machines and an actual velocity of the drive shaft of the one of the pressing machines. This is because there can be detected at which angle in the drive shaft of the one of the pressing machines with the clutch thereof being precedingly engaged, the clutch in the other of the pressing machines should be engaged, based on the engagement property of the clutch in the other of the pressing machines as well as the actual velocity of the drive shaft in the one of the pressing machines.
One technique of determining the timing of clutch engagement may be that the timing of clutch engagement in the other of the pressing machines is determined according to information obtained by time integrating the actual velocity, through time required for a velocity equal to the actual velocity of the drive shaft of the one of the pressing machines is obtained by the other of the pressing machines, based on the engagement property of the clutch after the clutch of the other of the pressing machines has been engaged.
According to a second aspect of the present invention, it provides a pressing machine comprising:
a motor;
a clutch which intermittently transmits a torque of a flywheel driven by the motor to the pressing machine;
a drive shaft which drives a slide by a power transmitted through the clutch;
first detection device which detects actual velocity information of the motor;
second detection device which detects actual rotational-position information of the drive shaft;
first generating device which generates reference velocity information of the motor;
second generating device which generates reference rotational-position information of the drive shaft, based on the reference velocity information;
compensation device which compensates the reference velocity information at a time of engagement of the clutch, based on a difference between the actual rotational-position information and the reference rotational-position information; and
a motor drive controlling circuit which controls drive of the motor, based on the actual velocity information and the reference velocity information when the clutch is de-engaged, and based on the actual velocity information and the reference velocity information compensated by the compensation device when the clutch is engaged.
Such a pressing machine may be used to carry out the aforementioned method of controlling synchronous drive of a plurality of pressing machines according to the present invention in an optimal manner.
The first generating device may include a first compensation block which compensates so as to alleviate a velocity change rate when the reference velocity information includes the velocity change. This is because the motor can be prevented from being overloaded by driving the motor within its rating, as described.
The second generating device may include a second compensation block which compensates the reference rotational-position information within a predetermined time period immediately after the clutch is engaged, based on an engagement property of the clutch. The drive control, thus can be carried out smoothly after the clutch engagement, too.
Moreover, the second generating device may include:
a first generating block which generates unit-rotational-position information of the drive shaft per predetermined unit time, based on the reference velocity information from the first generating device; and
a second generating block which generates reference rotational-position information by integrating the unit-rotational-position information per predetermined time period.
According to a third aspect of the present invention, it provides a method of controlling synchronous drive of a plurality of pressing machines, each of the pressing machines having a motor, a drive shaft to which a torque output of a flywheel driven by the motor is transmitted through a clutch and a slide driven by the drive shaft so that a rotational position of the drive shaft of each of the pressing machines has phase difference from each other, the method comprising:
a first step of setting reference velocity information of each of the motors in the pressing machines;
a second step of generating reference rotational-position information of each of the drive shafts, based on the reference velocity information;
a third step of setting a phase difference with respect to the reference rotational-position information of at least one of the pressing machines;
a fourth step of engaging the clutch of each of the pressing machines; and
a fifth step of controlling drive of the motor in each of the pressing machines,
wherein the fifth step carried out in each of the pressing machines comprises the steps of:
detecting actual velocity information of the motor;
detecting actual rotational-position information of the drive shaft;
comparing the actual rotational-position information with the reference rotational-position information;
compensating the reference velocity information into characteristic reference velocity information of each of the pressing machines, based on a result of the comparison; and
controlling drive of the motor, based on the characteristic reference velocity information and the actual velocity information, and
wherein the fifth step carried out in the at least one of the pressing machines to which the phase difference is set, further comprises a step of phase-shifting the reference rotational-position information by the phase difference set in the third step, and the phase-shifted reference rotational-position information and the actual rotational-position information are compared in the comparing step.
In addition to the aforementioned functions, such an arrangement is to phase-shift the reference rotational-position information by the phase difference set for at least one of the pressing machines. When the synchronization is controlled based on the result of comparison between the phase-shifted reference rotational-position information and the actual rotational-position information, the control of synchronization can accurately be realized while maintaining the phase differences.
The fifth step may be carried out in the at least one of the pressing machines to which the phase difference is set includes a step of setting a rate of gradually applying the phase difference. Thus, the phase difference may be changed during operation of that pressing machine by gently changing the phase difference in such a manner.
The third step may further comprise:
a step of detecting stoppage angle information of the drive shaft of each of the pressing machines before the clutch of each of the pressing machines is engaged; and
a step of determining an engagement sequence of the clutch of each of the pressing machines, based on the stoppage angle information of the drive shaft of each of the pressing machines and based on the phase difference.
In such a manner, the control of synchronous drive can be initiated while maintaining the phase difference, even though the drive shaft in each of the pressing machines synchronously driven with a phase difference has been stopped with that phase difference.
According to a fourth aspect of the present invention, it provides a pressing machine comprising:
a motor;
a clutch which intermittently transmits a torque output of a flywheel driven by the motor to the pressing machine;
a drive shaft which drives a slide by a power transmitted through the clutch;
first detection device which detects actual velocity information of the motor;
second detection device which detects actual rotational-position information of the drive shaft;
first generating device which generates reference velocity information of the motor;
second generating device which generates reference rotational-position information of the drive shaft, based on the reference velocity information;
phase difference setting device which sets a phase difference to the reference velocity information;
compensation device which compensates the reference velocity information at a time of engagement of the clutch, based on a difference between the actual rotational-position information and the reference rotational-position information to which the phase difference is set; and
a motor drive controlling circuit which controls drive of the motor, based on the actual velocity information of the motor and the reference velocity information when the clutch is de-engaged, and based on the actual velocity information of the motor and the reference velocity information compensated by the compensation device when the clutch is engaged.
Such a pressing machine may be used to carry out the aforementioned method of controlling synchronous drive of a plurality of pressing machines according to the present invention in a preferable manner.
According to a fifth aspect of the present invention, it provides a method of controlling synchronous drive of a plurality of pressing machines, each of the pressing machines having a motor, a drive shaft to which a torque of a flywheel driven by the motor is transmitted through a clutch and a slide driven by the drive shaft so that a rotational position of the drive shaft of each of the pressing machines is synchronous each other, the method comprising:
a first step of setting reference velocity information of each of the motors in the pressing machines;
a second step of engaging and de-engaging the clutch of each of the pressing machines;
a third step of transforming a velocity change rate within the reference velocity information set in each of the pressing machines into a first velocity change rate alleviated with a first rate when the clutch is de-engaged, and into a second velocity change rate which is further alleviated from the first velocity change rate with a second rate when the clutch is engaged;
a fourth step of generating reference rotational-position information in each of the pressing machines, based on the reference velocity information having the first or the second velocity change rate;
a fifth step of controlling drive of the motor in each of the pressing machines when the clutch is de-engaged; and
a sixth step of controlling drive of the motor in each of the pressing machines when the clutch is engaged,
wherein the fifth step carried out in each of the pressing machines comprises the steps of:
detecting actual velocity information of the motor; and
controlling drive of the motor, based on the actual velocity information and the reference velocity information having the first velocity change rate,
wherein the sixth step carried out in each of the pressing machines comprises the step of:
detecting actual velocity information of the motor;
detecting actual rotational-position information of the drive shaft;
comparing the actual rotational-position information with the reference rotational-position information;
compensating the reference velocity information having the second velocity change rate into characteristic reference velocity information of each of the pressing machines, based on a result of the comparison; and
controlling drive of the motor, based on the characteristic reference velocity information and the actual velocity information.
The reference velocity information may be common to the motors in the pressing machines.
In addition to the aforementioned functions, the present invention transforms the velocity change rate in the reference velocity information into the first velocity change rate alleviated by the first rate to use the full torque power of the motor for accelerating/decelerating the flywheel when the clutch is de-engaged and into the second velocity change rate further alleviated from the first velocity change rate when the clutch is engaged. When the clutch is de-engaged, thus, the acceleration/deceleration time, set-up time and waiting time can be reduced by fully using the torque power within the range of motor rating for accelerating/decelerating the flywheel. When the clutch is engaged, on the other hand, the acceleration/deceleration time may be extended to change the velocity during operation while maintaining the function of restoring the release of flywheel energy on each pressing and the accuracy of synchronous control.
When the velocity change rate in the reference velocity information includes an acceleration change rate and a deceleration change rate, each of the first and second rates may be set so that a rate of alleviating the acceleration change rate is higher than a rate of alleviating the deceleration change rate. On the deceleration, the velocity change rate is not required to be alleviated as much as the acceleration since the load on the motor may be used as a braking force.
The aforementioned sixth step may include a step of compensating the reference rotational-position information within a predetermined time period immediately after the clutch of each of the pressing machines is engaged, based on an engagement property of the clutch in one of the pressing machines. Alternatively, the aforementioned sixth step may includes a step of compensating the reference rotational-position information within a predetermined time period immediately after the clutch of each of the pressing machines is engaged, based on an engagement property of the clutch, which is characteristic of each of the pressing machines. Thus, the position of the drive shaft can smoothly be controlled immediately after the clutch-on.
According to a sixth aspect of the present invention, it provides a pressing machine comprising:
a motor;
a clutch which intermittently transmits a torque of a flywheel driven by the motor to the pressing machine;
a drive shaft which drives a slide by a power transmitted through the clutch;
first detection device which detects actual velocity information of the motor;
second detection device which detects actual rotational-position information of the drive shaft;
first generating device which generates reference velocity information of the motor;
velocity-change-rate alleviating device which transforms a velocity change rate in the reference velocity information into a first velocity change rate alleviated by a first rate when the clutch is de-engaged and into a second velocity change rate further alleviated from the first velocity change rate by a second rate when the clutch is engaged;
second generating device which generates reference rotational-position information of the drive shaft, based on the reference velocity information having the first or the second velocity change rate;
compensation device which compensates the reference velocity information having the second velocity change rate at a time of engagement of the clutch, based on a difference between the actual rotational-position information and the reference rotational-position information; and
a motor drive controlling circuit which controls drive of the motor, based on the actual velocity information and the reference velocity information having the first velocity change rate when the clutch is de-engaged, and based on the actual velocity information and the reference velocity information compensated by the compensation device when the clutch is engaged.
Such a pressing machine may be used to carry out the aforementioned method of controlling synchronous drive of a plurality of pressing machines in a preferable manner.
Even in such a pressing machine, each of the first and the second rates may be set so that a rate of alleviating the acceleration change rate is higher than a rate of alleviating the deceleration change rate .